a. Field
The disclosure relates to toner for use in electrophotographic image forming, such as copying and printing. The disclosure further relates to methods of making toner for use in electrophotographic image forming and methods for electrophotographic image formation using toner.
b. Description of the Related Art
Printing and copying processes are widely used to reproduce and disseminate, for example, legal documents, news documents, and correspondence between parties. Conventional printing and copying processes affix an image representing characters of a written language or pictures onto a substrate such as a sheet of paper. Most modern electrophotographic printing and copying processes use a toner to form the images that appear on a document. The toner is most often darkly colored, e.g., black, to show on a white or light background.
In general, toners provide only a temporary image, for example, many copied and/or printed documents are only read or viewed a few times and then discarded. Likewise, most copied documents are stored for only short periods of time before they are discarded. Discarded documents containing toner-based images are usually permanently destroyed through processes such as biodegradation, burning, or recycling.
Recycling is commonly used to reuse the substrate upon which an image is formed. There is no widespread recycling of toners from printed images. Toners on the other hand often undergo chemical and/or physical changes during the image formation process making recycling economically viable only in rare cases. The amount of toner needed to form a single letter-size image is almost insignificant in comparison to the mass of the substrate, e.g., less than 0.1 gram for a letter-sized image. However, the cumulative amount of toner used annually on a worldwide basis is substantial.
Most conventional toners contain one or more thermoplastic components. Typically, the thermoplastic components include a synthetic polymer such as, for example, a polyester. Most polyesters are synthetic, e.g., manufactured from refined materials. The monomers used to make the polyester resins used in toners are almost universally derived from mineral oil sources and are thus referred to as petroleum-based or synthetic monomers. Most mineral oils are thought to be fossilized plant and animal organisms but are not biologically-based or characterized as renewable resources.
There is a trend in developed countries to utilizing renewable resources as components that are consumed in business processes. For example, certain biologically derived polymers, such as cellulose-based polymers, have been suggested as substitutes for the petroleum-based polymeric materials conventionally used in toners.
Because toners are used in such great quantities worldwide, the substitution of synthetic petroleum-based polymers for biologically derived thermoplastics may provide a way to substantially reduce the use of petroleum resources and/or other non-renewable resources. Published patent application U.S. 2007/0015075 (incorporated herein by reference in its entirety) discloses deinkable toner compositions that include biologically-derived components. Deinkable toners are described that contain a thermoplastic polymer and a protein material, each of which is made from at least partially naturally-derived renewable sources such as soybeans. The naturally-derived thermoplastic polymers are made by reacting a soybeans-derived dimer acid with a synthetic diol component to form a polyester-type thermoplastic material. The thermoplastic polymer may contain other biologically-derived components, e.g., monomer units, such as amino acids, in addition to the biologically derived di-acid and/or diol.
Published patent application U.S. 2008/0227002 (incorporated herein by reference in its entirety) discloses toners that include polyester resins. The polyester resins may contain biologically derived di-acid monomer units such as lactic acid.
Published patent application U.S. 2008/0145775 (incorporated herein by reference in its entirety) describes thermoplastic resins synthesized from bio-based materials. The resins may include one or more bio-based monomers that increase the content of the renewable resource materials from which the toner is made.
The inclusion of bio-based components, such as bio-based monomer units, in the thermoplastic resins used in toners is often hindered by difficulties associated with purity, stability, and cost of bio-derived materials. For example, thermoplastic resins made from one or more biologically derived monomer units may suffer from variances in physical properties that are related to the purity and/or physical properties of the biologically-derived monomer units present in their reacted form in the thermoplastic resin. Thus, conventional bio-based resins toners have so far not been proven to be of practical use and have further not been proven to provide exemplary image forming characteristics.